Covalently modification of DNA by diolepoxides metabolically formed from polycyclic aromatic hydrocarbons(PAHs) such as benzo[a]pyrene (BaP) provides a mechanism for the genotoxicity, mutagenicity, and carcinogenicity of PAHs. Using NMR and molecular modeling we have showed that the hydrocarbon of the BaP modified DNA intercalates into the DNA helix that resulted in a bending of the helical axis at the modified site. The orientation of hydrocarbon is influenced by the absolute configuration at the C10 position of the BaP. The hydrocarbon is oriented toward the 5 end of the modified strand for DNA with a 10R dA adduct and the 3 end for a 10S dA adduct. Multiple conformations, for examples, with syn and anti glycosidic torsion angles at the modified dA residue, also are observed in some of the modified DNA. We are currently investigating the effect of sequence context at the modified site on the conformation of the modified DNA. These include DNA duplexes containing -GA*C-, -CA*C- and -CA*G- sequences in the modified strand with their corresponding complimentary strands. We also extend the study to DNA containing amino alcohol adduct (BaP lacking hydroxyl groups at the C7 and C8 positions). This may provide information on the role that these hydroxyls play in the structure of the modified DNA. These studies are currently in progress.C13 and Mass spectrometry were used to study the metabolic flux in E. coli BL21 and JM109 cells which were grown in C13 uniformaly labeled glucose. Using these techniques we have determined the C13 isotopomer distributions of oxaloacetate and acetyl-CoA in these cells. We found that in BL21, the glyoxylate shunt is active at 22% of the flux through the TCA cycle, and is inactive in JM109. Futher, in BL21, the flux through the pyruvate anaplerotic shunt equals that through the TCA cycle, while it operates at a third of the TCA cycle fulx in JM109. - NMR/molecular structures and interactions (drugs, DNA and proteins)